Semiconductor components are typically formed of a semiconductor device die and one or more leads and wire bonds for making electrical connection from the lead to the device die via a metal contact on the device die. Wire bonding processes for high current devices are slow and difficult to test where several bonds are used in parallel. In addition wire bonds may result in unreliable contacts. Furthermore, the electrical performance of the semiconductor component may suffer from parasitic resistances and inductances caused by the wire bonds. In applications such as switch mode power supplies, electro-static discharge protection devices or transient voltage suppression devices, or other applications having large current variations, large voltage spikes may occur due to the inductances in the wire bond. In addition in high current applications (typically in the order of amps) device heating may cause the wire bonds to degrade.
As an alternative to wire bonds the leads may comprise a clip portion for bonding to the semiconductor device die. This arrangement is known as a clip bond and compared to wire bonds may result in improved electrical and thermal performance of the semiconductor component and more reliable contacts.
When clip bonding to a semiconductor die via a metal contact, a solder may be used to complete the electrical and mechanical connection. As is well known in the art, the solder may be in the form of a paste comprising a proportion of lead, tin and silver powder in addition to other additives such as flux medium. However, such an arrangement can suffer from a number of problems such as the device die and clip not aligning properly, which can result in short circuits, and a solder layer thickness which can result in voids within the solder paste. During soldering processes, such as reflow processes (which are known in the art) evaporating gasses cannot escape from the voids and may result movement of the die with respect to the clip, again causing misalignment. Such void may also reduce the mechanical and/or electrical integrity of the connection.
A known lead 1 comprising a clip portion 2 bonded to a semiconductor device die 3 is shown in FIGS. 1a and 1b. As shown, the clip portion 2 comprises a major surface 8 which may be directly adjacent the semiconductor die 3 when the lead 1 fixed to a semiconductor device die 3. The clip portion 2 includes a contact portion 9 which is arranged to be mechanically and electrically connected using an appropriate solder material to appropriate metal contacts (not illustrated) pre-formed on the semiconductor device die 3.
Including the disadvantages mentioned above the illustrated arrangement and other known arrangements may also suffer from the problem that the integrity of the solder connection between the semiconductor device die and the clip may only be inspected from the side which may result in slower production through-put. In large scale industrial process it is advantageous to inspect from above using, for example a microscope. In addition observations have found that the semiconductor device dies may not correctly align with the clip portion, which could result in short circuits on the semiconductor die, thus rendering the semiconductor component inoperable.